#!/bin/bash

echo "Hello World!" 

echo "$0"
echo "$1"
echo "$2"

echo "$*"
echo "$@"

echo "$#"

A=123

B="A的值:$A"
C='A的值:$A'
D=1+2

readonly A

export A

echo "$?"

unset A

echo "$?"

echo "$A"
echo "$B"
echo "$C"
echo "$D"
